Release: Update changelog with 7.0.6

CHANGELOG.md

+# 7.0.6 (2020-07-09)
+
+### Bug fixes
+
+* **Templating**: Fixed recursive queries triggered when switching dashboard settings view [#26137](https://github.com/grafana/grafana/pull/26137)
+* **Templating**: Fix recursive loop of template variable queries when changing ad-hoc-variable [#26191](https://github.com/grafana/grafana/pull/26191)
+* **Auth**: Add support for forcing authentication in anonymous mode and modify SignIn to use it instead of redirect [#25567](https://github.com/grafana/grafana/pull/25567)
+* **Auth**: Fix POST request failures with anonymous access [#26049](https://github.com/grafana/grafana/pull/26049)
+
 # 7.1.0-beta 2 (2020-07-02)
 
 ### Features / Enhancements